Conventionally, there is a method for an operator to actually teach the sequence of movement and operation of a robot by using a teaching operation panel or the like as a method of teaching an operation to the robot and the like.
The teaching operation panel is provided with an emergency stop switch for urgently stopping the operation of the robot to protect the operator from danger caused by the operation of the robot while a teaching operation is being carried out.
FIG. 3 shows a conventional emergency stop circuit diagram for a robot, including an emergency stop switch disposed on a teaching operation pane 1. The teaching operation panel 51 is comprises a portable robot teaching device disposed such that it can be operated in the vicinity of the robot 52. The teaching operation panel 51 includes an emergency stop switch SW7, dead man switch SW8 and effective/ineffective switch SW9. The emergency stop switch SW7 comprises a normally-closed type push button switch for urgently stopping the operation of the robot 52 prior to the other switches regardless of the operation thereof. The dead man switch SW8 comprises a normally-open type push button switch mounted on the back surface of the teaching operation panel 51 for urgently stopping the robot 52 to secure the safety of an operator in such a manner that when the operator removes his hand from the teaching operation panel 51 and releases the pushed buttons the robot 52 is urgently stopped. The effective/ineffective switch SW9 comprises a changeover switch for making the function of the dead man switch SW8 either effective or ineffective.
The teaching operation panel 51 is connected to a robot control device (not shown) for controlling the operation of the robot 52 through connection cable, and in particular, the emergency stop switch SW7, the dead man switch SW8 and the effective/ineffective switch SW9 of the teaching operation panel 51 are connected to the relay circuit unit 53 in the robot control device. The power supply Vcc of the relay circuit unit 53 is connected to the dead man switch SW8 and effective/ineffective switch SW9 through the emergency stop switch SW7. A relay R1, connected in series to the dead man switch SW8, includes a make contact r1a and a break contact r1b, and a relay R2, connected in series to the effective/ineffective switch SW9, includes a make contact r2a and break contact r2b. Further, a relay R3, connected in series to a plurality of switches SW10-SWn mounted on a safety fence and connected to each other in series, includes two make contacts r3a1 and r3a2.
The three contacts, i.e., break contact r1b of the relay R1, the break contact r2b of the relay R2 and the make contact r3a2 of the relay R3 are connected to each other in parallel (which are tentatively referred to as a first parallel circuit), and the series circuit comprising the make contact r3a1 of the relay R3 and the make contact r2a of the relay R2 is connected in parallel to the make contact r1a of the relay R1 (which are tentatively referred to as a second parallel circuit). Then, the second parallel circuit, the first parallel circuit and a relay R4 are connected in series to each other and further connected to the power supply Vcc of the relay circuit unit 53. The make contact r4a of the relay R4 is disposed between a power source 54 and a brake release circuit 55, and when closed, the make contact r4a actuates the brake release circuit 55 and releases a brake applied to the operation of the robot 52 and thus the robot 52 is in operation. Further, the power supply Vcc of the relay circuit unit 53 is connected to the series circuit comprising the safety fence switches SW10-SWn and relay R3.
In this robot emergency stop circuit, when the dead man switch SW8 of the teaching operation panel 51 is depressed and the effective/ineffective switch SW9 is set to an effective side (the switch is opened), the relay R1 is actuated to close the make contact r1a and the relay R2 is not actuated and thus the break contact r2b is in a closed state. Therefore, the relay R4 is actuated to close the make contact r4a. With this arrangement, power is supplied from the power source 54 to the brake release circuit 55 so that the brake release circuit 55 releases a brake and thus the robot 52 is in operation. In this case, the robot 52 is operated notwithstanding the fact that the safety fence is opened or closed.
Further, when the effective/ineffective SW9 is set to an ineffective side (the switch is closed) and the safety fence is closed (the switches SW10-SWn are closed), the relays R2 and R3 are actuated. Therefore, the make contacts r2a, r3a1 and r3a2 are closed and the relay R4 is actuated. With this arrangement, the make contact r4a is closed and power is supplied from the power source 54 to the brake release circuit 55, and thus the robot 52 is in operation.
In this case, when the safety fence is opened and the switches SW10-SWn are opened, the relay R3 is not actuated and the make contacts r3a1 and r3a2 are opened and thus the operation of the relay R4 is stopped notwithstanding that the dead man switch SW8 is opened or closed. Therefore, the make contact r4a is opened and power is not supplied from the power source 54 to the brake release circuit 55 and thus a brake is applied to the robot 52 to stop the operation thereof.
Note, when the emergency stop switch SW7 is actuated, the relays R1 and R2 are not actuated regardless of the state of the dead man switch SW8 and effective/ineffective switch SW9, and thus the robot 52 is urgently stopped.
As described above, the emergency stop circuit is arranged to protect the operator from danger caused by the operation of a robot while a teaching operation is carried out.
Nevertheless, the aforesaid above-described robot emergency stop circuit is arranged such that when the teaching operation panel 51 is removed from the robot control device and the respective switches SW7, SW8 and SW9 of the teaching operation panel are disconnected from the relay circuit unit 53, the relays R1 and R2 are not actuated, and thus the robot 52 is urgently stopped.
Therefore, a problem arises when the teaching operation panel 51, disposed in the vicinity of the robot 52, is to be disconnected from the robot control device when a teaching operation to the robot has been completed through the teaching operation panel 51. Because the teaching operation panel 51 is not necessary for the automatic operation of the robot 52 after the completion of the teaching operation, it is desired to disconnect the teaching operation panel 51 from the robot control device. However, if the teaching operation panel 51 is disconnected from the robot control device, the robot 52 is urgently stopped.